The present invention relates to the present applicant's prior patent, U.S. Pat. No. 4,063,890, issued Dec. 20, 1977, entitled "METHOD AND APPARATUS FOR STERILIZING AND STORING CONTACT LENSES", issued to Neville A. Baron.
As noted in applicant's prior patent, the prior art was directed toward sterilization of contact lenses by means of chemical treatment, boiling and the like, of such lenses, especially with respect to soft contact lenses which are characteristically referred to as hydrophilic lenses, owing to the presence of a substantial proportion of aqueous material in their body structure. However, the prior art appears to have had little, if any, appreciation for the need to destroy microorganisms which can be present on the surface or in the body of lenses.
Recent discoveries by applicant during the course of his professional practice as an eye physician, reveal that various patient allergies have arisen from and are traceable to the presence of various chemicals used in connection with commonly used and accepted liquid medium utilized to sterilize eye lens bodies. In addition, certain of the prior art liquid media containing seemingly harmless chemical additives or preservatives have been banned totally from use in some countries, because of their known carcinogenic causing properties.
Still further, it has been determined that most, if not all, prior art sterilization media are susceptible to microorganism invasion and growth if not adequately protected therefrom. The foregoing health hazardous aspect of the prior art processes and liquid media illustrate only a few of the reasons for needed solutions and improvements in the field of lens body asepticization. A detailed inquiry into prior art techniques suggest a clear lack of understanding and appreciation of the seriousness of the voids and problems which exist with respect to the prior art. More, specifically, it can be readily appreciated that there is a need to provide means for asepticizing eye lens bodies which eliminate the misinterpretation by patients as to chemical and process aspects thereof.
Applicant's prior process and apparatus were primarily directed toward "soft" contact lenses and the use of ultraviolet irradiation at a wavelength longer than 221 nanometers, and preferably longer than 240 nanometers, but implicitly below the undesirable wavelength of 254 nanometers. The time duration of radiation exposure was not specifically stated, except that such exposure duration should be such as not to shorten the half-life of the polymeric soft lenses. More particularly, the prior art recognized that ultraviolet irradiation of soft lenses in their peak absorption spectrum range, i.e. 253.7 nanometers wavelength, during repeated cycles or continuous exposure for relative short periods would cause molecular deterioration thereof. In addition, the prior art appears devoid of any knowledge or appreciation for the need to destroy micro-organisms associated with contact eye lenses to thereby safeguard against diseases to the eyes or other parts of the human body which may be caused by the presence of such organisms on the surface or in the body of all lenses for the eyes, which may enter the human body through the eyes. Consequently, the focus of the prior art was solely to sterilize the lenses and their storage containers so as to avoid perceptive damage or deterioration to the contact lenses, while ignoring the very important health and possible disease aspect of the problem, which might be caused by the presence of micro-organisms not destroyed by the prior art sterilization processes and materials.
Heretofore, as noted in applicant's prior patent, it was thought in the prior art, that ultraviolet irradiation below the 254 nanometers wavelength, i.e. around 220 to 240 nanometers wavelength was the direction to go. However, after considerable research and investigation applicant has discovered the direction to go is significantly above 254 nanometers wavelength, i.e. in the 290 to 310 nanometers wavelength range. More specifically, applicant has discovered that the peak absorption spectrum of the aromatic amino acids, in particular tryptophan which is an amino acid component that is essential to growth and nutrition of micro-organisms is at about the 295 nanometers wavelength. Thus, by irradiating these organisms containing the tryptophan component it can be destroyed readily.
Applicant, after extensive investigation and research, has discovered that the absorption rate of lenses made of polymethylmethacrylate in the 290 to 400 nanometers range, is on the order of 20% to 25% which causes minimal shortening of the half-life of lenses made with these related materials. Lens which do not have this material tend to absorb energy even less in this wavelength range.
It is worth noting that all eye contact lens bodies have an inherent half-life due to their exposure to normal sunlight exposure during daily use.
As a result of these discoveries, applicant contends that an appropriate solution to the prior art problem is the use of ultraviolet irradiation spectrum in the range of 290 to 310 nanometers wavelength, so as to effectively destroy micro-organisms rapidly, as the criteria or standard for asepticization, while simultaneously avoiding any perceptive damage to a wider range of contact lenses than heretofore considered possible or realizable in the prior art.